【作者】 王昊宇；

【导师】 刘俊秋；

【作者基本信息】 吉林大学 ， 高分子化学与物理， 2011， 博士

【摘要】 富勒烯一经被人们发现,就引起了科学工作者极高的研究热情,由于其自身独特的结构,使得它具有超导、铁磁、润滑、光电导体、催化、生物制药等性质。有着“自由基海绵”之称的富勒烯,具有能够淬灭多种自由基的能力,而且其效能已经超过了传统的抗氧化剂,这使得它在生物制药领域有着很高的研究价值,C₆₀作为富勒烯家族的主要代表,自然成为这方面研究的重点对象。然而C₆₀具有强疏水的性质,这大大阻碍了人们对它生物活性的研究,因此,如何得到水溶性较好的富勒烯便成为人们要解决的首要问题。为了解决其水溶性,化学工作者们用多种水溶性基团对富勒烯进行修饰,以达到使其水溶的目的。近年来,随着超分子科学和纳米科学的深入发展,利用纳米尺度的富勒烯作为构筑基元来设计复杂的超分子复合物成为很重要的研究领域。基于对超分子自组装和抗氧化酶的理解,我们开展了C₆₀衍生物的超分子组装工作,并研究了这些超分子复合物的抗氧化生物活性:1.温度响应的C₆₀超分子复合物的构建环糊精和金刚烷作为一对经典的主客体分子,已被广泛的应用于各种超分子结构的构筑。近年来,具有刺激响应性质的聚合物成为了聚合物领域研究的又一热点,因此,我们将这一概念引入到我们的体系中,以期望得到具有刺激响应的超分子复合物。为此,我们设计合成了带有环糊精单体的温敏性聚合物,和带有金刚烷基团的C₆₀衍生物,通过溶剂极性的调节使聚合物中的环糊精对金刚烷部分进行识别和包结,从而形成超分子复合物,并且这种复合物继承了聚合物温度响应的性质。由于复合物中C₆₀极强的疏水性质,使得其在水相中能够自聚集成囊泡结构,而且由于复合物具有温敏性质,这种囊泡结构可以随着温度的变化而发生改变,成为实心球状粒子。富勒烯都具有很强的淬灭自由基的能力,我们所制备的C₆₀复合物同样也具备这样的功能。我们以淬灭羟基自由基为例,发现复合物可以有效的消除Fenton反应中产生的羟基自由基,并且随着温度变化引起的聚集体形貌变化还会影响到其淬灭效率。除此之外,我们还在亚细胞水平研究了复合物的生物学效应,证明这种复合物一定程度上可以保护线粒体免受自由基的损害。2.两亲性C₆₀衍生物的自组装大多数两亲性的富勒烯衍生物,在水相中能够自发的形成自聚集体,全碳的富勒烯球的强疏水性成为了其自组装的主要驱动力,因而很多富勒烯衍生物可以在水相中形成一定的组装结构。我们所制备的C₆₀衍生物tetra-Ad-C₆₀,由于在支链上连有缩醇基团,因此它也具备两亲性,并在水相中的聚集体以一定形貌存在。通过DLS、SEM和TEM的表征,证明tetra-Ad-C₆₀在水中自聚集成囊泡结构。此外,通过桥联环糊精的作用,还可以将水相中的囊泡连接起来,形成更大的聚集结构。3.基于超分子组装构建具有GPx活性的C₆₀衍生物利用环糊精与金刚烷间经典的主客体识别作用,可以将C₆₀溶于水相中,而环糊精较易容易修饰,可以将很多功能基团键联在环糊精分子上,因此,我们将GPx酶的活性位点引入其中,进而制备出具有双功能的C₆₀复合物。这种复合物同样能够有效的淬灭体系中的羟基自由基,保护线粒体免受损伤,同时该酶模型也展现出了较高的GPx催化活力,与著名小分子硒酶模拟物Ebselen相比,有了24倍的提高。与先前报道的同类酶模型相比,该酶模型制备简单,催化活性显著,充分体现了以自组装方法构筑人工酶的优势。更多还原

【Abstract】 Fullerene, as the third carbon allotrope, has attracted increasing attention because of its exciting physical and chemical properties, which endow fullerene-containing materials with broad and promising applications in superconductor, ferromagnet, lubrication, photoconductor, catalysts, and molecular medicines. C60, the most representative member of the fullerene family, has been studied in various fields of biomedicine for its unique properties. As a“free radical sponge”, C60 has been demonstrated excellent ability to quench various free radicals more efficiently than conventional antioxidants. Furthermore, many fullerene-based compounds prepared artificially have shown potential practical value, for instance, reduction of injury on ischemic reperfusion of the intestine, a decrease in number of cells undergoing apoptosis, reduction in free radical levels in organ perfusate, and neurprotective effects. Though, in recent years, people are having much more interest in studying potential bioactive water-soluble fullerene derivatives emphasizing on their capacity to quench free radicals, the extreme hydrophobicity is a serious barricade for the broad prospects on bio-medical research and application. Therefore, a mass of representative works focus on functionalizing fullerene with negatively charged carboxylic, positively charged quaternary ammolonium, and non-charged functional group as ethylene glycol groups and polymers, etc. to enhance the water solubility of fullerenes. Another approach to overcome the insolubility is to encapsulate the respective monomer species in supramolecular structure with host moiety, such as cyclodextrin, surfactants, gels, or polymers, etc. Besides those approaches, fullerene can be stabilized in water as nano-scale colloidal assemblies through routes. For example, nanoscale colloid of C60 can be formed in the following steps. Firstly, dissolve C60 in water-miscible polar organic solvents such as tetrahydrofuran (THF) and mix with water, subsequently remove the transfer solvent via distillation or dialysis. However, the first two avenues seemed to be more promising in application of fullerene in biomaterial field.For the extreme hydrophobicity of C60, most of water-soluble derivatives of C60 are amphiphilic, while amphiphilic molecular organization is one of the widely used methods in supramolecular chemistry to construct nano-architectures. This method uses the balanced hydrophilic-hydrophobic structural motifs to give rise to micells, bilayers and further vesiclar structures, and its advantage makes it possible to solubilize the extremely hydrophobic C60 in polar media and to utilize the propensity of amphiphilic fullernenes to form prominent assemblies.1. Supramolecular complex of C60 derivative with ability of thermo-responseWe applied thermo-responsive copolymer consisting of host sites, which could recognize guest molecules, to conjugate insoluble derivative of C60 in contrast to conventional water-soluble C60, for the purpose of realizing its solubility. The fabrication of thermo-responsive assemblies was based on the complex consisting of thermo-responsive polymer and derivative of fullerene with adamantyl moiety. The complex can self-assemble to vesicles for its amphiphilic structure.It is noteworthy that the morphology of assemblies could be tuned reversibly from vesicles to nano-spheres when temperature changed. Furthermore, the assemblies have an excellent ability to scavenge hydroxyl radicals of biological system due to the introduction of the derivative of fullerene into the complex, and the scavenging efficiency could be obviously influenced by the change of temperature owing to the thermo-responsive property of the supramolecualr complex.2. Self-assambly of amphiphilic C60 derivativeLots of fullerene derivatives can self-assemble as some morphology in aqueous, because the all-carbon fullerene is completely hydrophobic and hydrphobicity can be the force to form assemblies. Tetra-Ad-C60, as a derivative of C60 that we synthetized, can self-assemble in aqueous for the ethylene glycol group which is hydrophilic. It was proved that tetra-Ad-C60 can self-assemble as vesicle in the method of DLS, SEM and TEM.. Furthermore, the vesicles can assemble as higher degree assemblies in the case of the presence of bridged cyclodextrin.3. Supramolecular derivative of C60 with GPx activityBeacuase cyclodextrin is easy to be derivated and many functional groups can be linked on it, we synthetized a derivative of cyclodextrin with GPx active site to construct supramolecules with C60 derivative. The complex we constructed can quench hydroxyl radicals efficiently for the fullerene moiety, and it can protect mitochondria from oxidative damage. Furthermore, the complex as a model of enzyme showed a high GPx activity and a remarkable rate enhancement of 24-fold compared to the well-known GPx mimic ebselen was observed. Compared with other bifunctional enzyme mimics, this supramolecular artificial enzyme has its obvious advantage: simple preparation process and remarkable catalytic activity.更多还原